1
Q
What are cocci?
A
Cocci are bacteria that are usually round but can also be oval, elongated, or flattened on one side.
2
Q
What happens to cocci after they divide?
A
They may remain attached to one another, forming characteristic arrangements.
3
Q
What are diplococci?
A
Cocci that divide in one plane and remain attached as pairs.
4
Q
What are streptococci?
A
Cocci that divide in one plane and remain attached in chain-like patterns.
5
Q
What are tetrads?
A
Cocci that divide in two planes and remain attached in groups of four.
6
Q
What are sarcinae?
A
Cocci that divide in three planes and remain attached in cubelike groups of eight.
7
Q
What are staphylococci?
A
Cocci that divide in multiple planes and form grapelike clusters.
8
Q
Why are cocci arrangements useful?
A
Group characteristics help identify and differentiate certain cocci.
9
Q
How do planes of division determine cocci arrangement?
A
The number and orientation of division planes determine whether cocci form pairs, chains, tetrads, cubes, or clusters.
10
Q
What determines the arrangement of cocci after cell division?
A
The number of planes of division and whether the cells remain attached after dividing.
11
Q
What cocci arrangement results from division in one plane when cells remain in pairs?
A
Diplococci
12
Q
What cocci arrangement results from division in one plane when cells form chains?
A
Streptococci
13
Q
What cocci arrangement results from division in three planes?
A
Sarcinae (cubelike groups of eight cells)
14
Q
What cocci arrangement results from division in multiple planes?
A
Staphylococci (grapelike clusters)
15
Q
Why are cocci arrangements useful in microbiology?
A
They help identify and differentiate types of cocci.
16
Q
How do planes of division determine cell arrangement?
A
The number and orientation of planes of division determine how cells remain attached after division, which creates different cell arrangements.
17
Q
Division in two planes
A
produces groups of four (tetrads).
18
Q
Division in three planes
A
produces cubelike packets of eight (sarcinae).
19
Q
What are single bacilli?
A
Rod-shaped bacteria that exist as individual cells after division.
20
Q
What are diplobacilli?
A
Bacilli that divide and remain attached in pairs.
21
Q
What are streptobacilli?
A
Bacilli that divide repeatedly in one plane and remain attached in chains.
22
Q
What are coccobacilli?
A
Short, oval-shaped bacilli that appear intermediate between cocci and bacilli.
23
Q
Why can bacilli form chains but not clusters?
A
Because bacilli divide in only one plane, allowing chain formation but preventing clustered arrangements.
24
Q
What is bacillus
A
It refers to a rod-shaped bacterial cell (a shape).
25
Why is the word bacillus confusing in microbiology?
Because it has two meanings: a cell shape (rod-shaped bacterium) a specific bacterial genus when capitalized and italicized.
26
What does Bacillus (capitalized and italicized) refer to?
A specific genus of bacteria.
27
Give an example of Bacillus as a genus.
Bacillus anthracis, the causative agent of anthrax.
28
How do Bacillus cells commonly appear morphologically?
They often form long, twisted chains of cells.
29
How can you tell whether 'bacillus' refers to shape or genus?
Lowercase, not italicized → bacterial shape Capitalized and italicized (Bacillus) → genus
30
What is a coccobacillus?
A coccobacillus is a bacterium that is oval or very short rod–shaped, appearing intermediate between cocci (round) and bacilli (rod-shaped).
31
What is the general shape characteristic of spiral bacteria?
Spiral bacteria have one or more twists and are never straight.
32
What are vibrios?
Vibrios are bacteria that look like curved rods.
33
What are spirilla (singular: spirillum)?
Spirilla are helical, corkscrew-shaped bacteria with fairly rigid bodies.
34
What are spirochetes?
Spirochetes are helical and flexible bacteria.
35
How do spirilla move?
Spirilla move using external flagella (propeller-like appendages).
36
How do spirochetes move?
Spirochetes move using axial filaments (twisting using internal flagella)
Spirochetes move by corkscrew motion using internal axial filaments
37
What is the distinguishing feature of spirochete bacteria?
Spirochetes are flexible, spiral shaped bacteria that move using axial filaments (internal flagella) located inside a sheath, not on the outside
38
What does pleomorphic mean in bacteria?
Pleomorphic bacteria are genetically capable of having many different shapes, not just one.
39
What is the glycocalyx in prokaryotes? *
The glycocalyx is a sticky outer coating on the outside of the cell wall of some bacteria
Helps cell attach, protect itself, and survive
viscous (sticky), gelatinous polymer external to the cell wall that surrounds the cell; it is composed of polysaccharide, polypeptide, or both.
40
Where is the bacterial glycocalyx made and where is it located?
It is made inside the cell and secreted to the cell surface, where it lies external to the cell wall.
41
What is a capsule?
A capsule is a glycocalyx that is organized and firmly attached to the cell wall.
42
What are flagella?
Structures that allow bacteria to move
Flagella are long, tail-like structures that help bacteria move by acting like propellers
43
What is the singular form of flagella?
Flagellum
44
What are bacteria called if they lack flagella?
Atrichous (without projections)
45
What is the glycocalyx in prokaryotes?
The glycocalyx is a viscous (sticky), gelatinous polymer external to the cell wall that surrounds the cell; it is composed of polysaccharide, polypeptide, or both.
46
Where is the bacterial glycocalyx made and where is it located?
It is made inside the cell and secreted to the cell surface, where it lies external to the cell wall.
47
What is a capsule?
A capsule is a glycocalyx that is organized and firmly attached to the cell wall.
48
What is a slime layer?
A slime layer is a glycocalyx that is unorganized and loosely attached to the cell wall.
49
How can the presence of a capsule be determined?
By using negative staining.
50
What is the glycocalyx in prokaryotes? *
The glycocalyx is a sticky outer layer that surrounds sone bacteria outside the cell wall
It is composed of polysaccharide, polypeptide, or both.
51
Where is the bacterial glycocalyx made and where is it located?
It is made inside the cell and secreted to the cell surface, where it lies external to the cell wall.
52
What is a capsule?
A capsule is a glycocalyx that is organized and firmly attached to the cell wall.
53
What is a slime layer?
A slime layer is a glycocalyx that is unorganized and loosely attached to the cell wall.
54
How can the presence of a capsule be determined?
By using negative staining.
55
What are flagella?
Flagella are long, filamentous appendages that propel bacteria.
56
What is the singular form of flagella?
Flagellum
57
What are bacteria called if they lack flagella?
Atrichous (without projections)
58
What does peritrichous mean?
Flagella are distributed over the entire surface of the cell.
59
What does polar flagella mean?
Flagella are located at one or both poles (ends) of the cell.
60
What does monotrichous mean?
A single flagellum at one pole of the cell.
61
What does lophotrichous mean?
A bunch of flagella at one pole of the cell
62
What does amphitrichous mean?
Flagella at both poles of the cell.
63
What are bacteria without flagella called?
Atrichous
64
What is the glycocalyx (capsule / slime layer) composed of?
Polysaccharides (sometimes polypeptides)
65
What is the main function of the glycocalyx?
Virulence factor
66
How does the glycocalyx help bacteria attach?
Helps bacteria attach to surfaces
67
How does the glycocalyx help bacteria avoid being killed by the immune system?
- Immune cells try to grab and eat bacteria
- The glycocalyx is slippery and sticky
- This makes it hard for immune cells to attach - phagocytosis is avoided
68
Which bacterium is an example of having a glycocalyx?
Streptococcus mutans
69
What surface does Streptococcus mutans attach to?
Teeth
70
What disease is caused by Streptococcus mutans?
Dental caries
71
What is the shape of bacterial flagella?
Straight, not wavy
72
Where are flagella located relative to the cell wall?
External to the cell wall
73
What protein are flagella made of?
Flagellin
74
How many main parts does a flagellum have?
Three parts
75
What is the filament of the flagellum?
External part made of flagellin protein
76
What is the hook of the flagellum?
Connects the filament to the base
77
What is the basal body of the flagellum?
Central rod with rings (screw-like structure)
78
What does monotrichous mean?
Single polar flagellum
79
What does amphitrichous mean?
One flagellum at each end
80
What does lophotrichous mean?
Bundle of flagella at one end
81
What does peritrichous mean?
Flagella all around the cell
82
What makes flagella unique in how they relate to the cell body?
Unique because of how they emerge from the cell body
83
What is the only human cell that has flagella?
Sperm cell
84
How do bacteria move?
Run and tumble
85
What is a “run” in bacterial movement?
Straight movement
86
What is a “tumble” in bacterial movement?
Abrupt direction change
87
Are bacteria motile?
Yes, bacteria are very motile
88
What is an axial filament also called?
Endoflagella
89
In what type of bacteria are axial filaments found?
Found only in spiral bacteria
90
Where is the axial filament located?
Inside the cell, wrapped around the cell (not sticking out)
91
What covers the axial filament?
Outer sheath
92
What type of movement does an axial filament cause?
Corkscrew motion
93
How does movement with an axial filament differ from flagella movement?
Moves forward only (no run/tumble)
94
What bacterium is an example of one with an axial filament?
Treponema pallidum
95
What disease is caused by Treponema pallidum?
Syphilis
96
What type of bacteria have axial filaments?
Spirochetes.
97
What are axial filaments also called?
Endoflagella.
98
Where are axial filaments located in spirochetes?
Beneath the outer sheath of the cell.
99
Where do axial filaments originate in the cell?
They arise at the ends of the cell.
100
How are axial filaments arranged within a spirochete?
They spiral around the cell beneath the outer sheath.
101
What is the structure of axial filaments similar to?
Flagella.
102
How do axial filaments produce movement in spirochetes?
By rotating, which causes movement of the outer sheath.
103
What type of movement do axial filaments produce?
Spiral (corkscrew-like) motion.
104
What common object is spirochete movement compared to?
A corkscrew moving through a cork.
105
Why is corkscrew motion advantageous for spirochetes?
It allows them to move effectively through bodily fluids.
106
Which disease-causing bacterium is mentioned as benefiting from axial filament movement?
Treponema pallidum.
107
What disease is caused by Treponema pallidum?
Syphilis.
108
What is another spirochete mentioned in the text, and what disease does it cause?
Borrelia burgdorferi, which causes Lyme disease.
109
How are axial filaments different from flagella in location?
Axial filaments are located beneath the outer sheath, whereas flagella are external appendages.
110
How do fimbriae compare to flagella in size and thickness?
Shorter and thinner than flagella
111
What is the shape of fimbriae?
Straight, hair-like
112
Where are fimbriae located relative to the cell wall?
External to the cell wall
113
Are fimbriae used for movement?
No, not for movement
114
What is the primary function of fimbriae? ***important
Attachment
115
Which bacterium uses fimbriae to attach to genital cells?
Neisseria gonorrhoeae
116
What structure does Neisseria gonorrhoeae use to attach to genital cells?
Fimbriae
117
What disease is caused by Neisseria gonorrhoeae?
Gonorrhea (STD)
118
What are sex pili used for?
Cell-to-cell attachment (not surface attachment)
119
What structure do sex pili form between bacteria?
A bridge between two bacterial cells
120
What is transferred through sex pili?
DNA
121
What is the process of DNA transfer via sex pili called?
Conjugation
122
What does conjugation lead to?
Genetic variation
123
How do sex pili contribute to antibiotic resistance?
Leads to antibiotic resistance (superbugs)
124
Can humans make peptidoglycan?
No, humans cannot make peptidoglycan
125
Where is peptidoglycan found?
Found only in bacteria
126
What sugars form the peptidoglycan backbone?
NAG (N-acetylglucosamine) and NAM (N-acetylmuramic acid)
127
How are NAG and NAM arranged in peptidoglycan?
NAG and NAM alternate to form the backbone
128
What are peptide cross-links composed of?
Short amino acid chains (tetrapeptides)
129
What do peptide cross-links connect in peptidoglycan?
Link NAM units together
130
What determines the strength of peptidoglycan cross-linking?
Strength is determined by genetics
131
How do bacteria move?
Bacteria move using flagella, axial filaments (endoflagella) in spirochetes, and pili through twitching or gliding motility. Different structures enable movement depending on the bacterial species and environment.
132
Why are bacterial capsules medically important?
Capsules enhance bacterial virulence by helping bacteria adhere to host tissues and protect themselves from host defenses. Their presence allows bacteria to colonize tissues and cause disease; without a capsule, colonization and infection are less likely.
133
Differentiate flagella, axial filaments, fimbriae, and pili.
Flagella: Long, filamentous appendages used for motility.
Axial filaments (endoflagella): Internal, corkscrew-like filaments found in spirochetes that enable spiral motion.
Fimbriae: Short, numerous hairlike structures used for attachment to surfaces and host tissues.
Pili: Longer and fewer than fimbriae; involved in motility (twitching/gliding) and DNA transfer during conjugation.
134
Describe the structure and function of the glycocalyx.
The glycocalyx is a viscous, sticky, layer external to the cell wall
composed of polysaccharide, polypeptide, or both
It is produced inside the cell and secreted to the surface. When organized and firmly attached
it is called a capsule; when unorganized and loosely attached
it is a slime layer. It helps with adhesion, protection, and biofilm formation.
135
Do humans ever make peptidoglycan?
No, humans never make peptidoglycan
136
What does the term peptidoglycan refer to?
Protein + sugar
137
Which organisms can make peptidoglycan?
Bacteria only
138
What basic sugar do bacteria start with to make peptidoglycan?
Glucose
139
What do bacteria do to glucose to form peptidoglycan sugars?
Modify glucose into a new form
140
What are the two modified sugars in peptidoglycan?
NAG and NAM
141
What does NAG stand for?
N = N-acetyl
A = acetyl
G = glucosamine
142
What does NAM stand for?
N = N-acetyl
A = acetyl
M = muramic acid
143
How are NAG and NAM arranged in peptidoglycan?
NAG and NAM join together to form the sugar backbone
144
What is the role of the peptide portion of peptidoglycan?
Holds the sugars together
145
What is the peptide portion made of?
Connecting chains of amino acids
146
How are the peptide chains arranged?
Chains criss-cross
147
Does polypeptide length stay the same?
No, polypeptide length varies
148
What is the usual length of the peptide chain?
Usually tetrapeptide
149
What do peptide chains ensure in peptidoglycan structure?
Ensure NAM units connect to each other
150
Are peptide linkages the main linkage in peptidoglycan?
No, they are not the main linkage
151
What does the peptide linkage connect?
Top NAM links to bottom NAM
152
What determines the number of amino acids in peptide chains?
Determined by genetics
153
Why do bacteria look so different from one another?
Differences come from simple structure and modified cell wall
154
What structural feature is mainly responsible for differences in bacterial appearance?
Modified cell wall
155
What is the bacterial cell wall?
The bacterial cell wall is a complex, semirigid structure that surrounds the plasma (cytoplasmic) membrane and is responsible for the shape of the cell.
156
What organisms have a bacterial cell wall?
Almost all prokaryotes have a cell wall that surrounds and protects the fragile plasma membrane.
157
What is the major function of the bacterial cell wall?
Its major function is to prevent bacterial cells from rupturing when the water pressure inside the cell is greater than that outside the cell.
158
Besides preventing rupture, what other functions does the bacterial cell wall have?
It helps maintain the shape of the bacterium and serves as a point of anchorage for flagella.
159
Why is the bacterial cell wall clinically important?
It contributes to the ability of some species to cause disease and is the site of action of some antibiotics.
160
How is the bacterial cell wall used in bacterial identification?
The chemical composition of the cell wall is used to differentiate major types of bacteria.
161
How do eukaryotic cell walls differ from prokaryotic cell walls?
Eukaryotic cell walls differ chemically, are simpler in structure, and are less rigid than prokaryotic cell walls.
162
How many layers of peptidoglycan are found in Gram-positive bacteria?
Several layers
163
How thick is the peptidoglycan layer in Gram-positive bacteria?
Thick PG layer
164
What unique component is found in the Gram-positive cell wall?
Teichoic acid
165
What is teichoic acid made of?
Carbon molecule (alcohol) + phosphate
166
What are the two types of alcohols found in teichoic acid?
Ribitol and glycerol
167
How many carbon atoms does ribitol have?
5 carbon atoms
168
How many carbon atoms does glycerol have?
3 carbon atoms
169
What charge do phosphate groups have?
Negative charge
170
What ions are attracted by teichoic acid phosphates?
Positive ions (Mg²⁺, Ca²⁺)
171
How does teichoic acid help the cell?
Helps with transport
172
How is teichoic acid used clinically or diagnostically?
Used to recognize bacteria and for species identification
173
Why is teichoic acid arrangement important?
Arrangement matters
174
What is wall teichoic acid?
Teichoic acid that stays in the cell wall
175
What is lipoteichoic acid?
Teichoic acid that goes into the plasma membrane
176
Why is the teichoic acid arrangement considered unique?
Very unique arrangement
177
Describe the overall structure of a Gram-positive cell wall.
Thick cell wall with plasma membrane underneath
178
Why are bacterial capsules medically important?
Bacterial capsules are medically important because they contribute to a bacterium’s ability to cause disease. Capsules protect bacteria from host defenses (such as phagocytosis) and help them survive in the body. Their presence can increase virulence, making infections more severe.
179
How do bacteria move?
Bacteria move using flagella, axial filaments (endoflagella), and pili. Flagella rotate to propel bacteria through liquid environments. Axial filaments (in spirochetes) rotate beneath an outer sheath, producing corkscrew motion. Pili enable movement such as twitching and gliding motility.
180
What kind of molecules are N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)?
NAG and NAM are carbohydrates. They are monosaccharides that alternate to form the carbohydrate backbone of peptidoglycan in bacterial cell walls.
181
What are the major structural differences between gram-positive and gram-negative cell walls?
Gram positive
- thick PG layer
- no outer membrane
Gram Negative
- thin PG layer
- outer membrane and LPS
182
Is the peptidoglycan layer thick in Gram-negative bacteria?
No, PG is not thick
183
How many layers of peptidoglycan are found in Gram-negative bacteria?
One or two layers only (never more)
184
Where is the peptidoglycan layer located in Gram-negative bacteria?
Between the plasma membrane and the outer membrane
185
What does the Gram-negative cell wall structure resemble?
Looks like a sandwich
186
What makes the Gram-negative outer membrane special?
Has qualities not found in humans
187
Why does the outer membrane make bacteria unique?
It has structures not found in human cells
188
How many important components does the Gram-negative outer membrane have?
Four
189
What is the role of phospholipids in the outer membrane?
Form the bilayer framework
190
What is the function of lipoproteins in the outer membrane?
Act as anchors
191
Why are lipoproteins important for outer membrane stability?
Prevent the outer membrane from floating
192
What are porin proteins?
Channels in the outer membrane
193
What is the function of porin proteins?
Open and close to let substances in
194
What is one major component of the Gram-negative outer membrane?
Lipopolysaccharide (LPS)
195
Where is lipopolysaccharide (LPS) found?
In the outer membrane of Gram-negative bacteria
196
What is Lipid A composed of?
Pure fat
197
What type of toxin is Lipid A?
Endotoxin
198
What symptoms can Lipid A cause?
Fever and GI problems (nausea, vomiting, diarrhea)
199
What severe conditions can Lipid A lead to?
Septic shock
200
Can Lipid A be fatal?
Yes
201
What is the polysaccharide portion of LPS?
Sugar chain
202
What is the function of the polysaccharide portion of LPS?
Used to recognize bacteria
203
What Gram-positive structure is equivalent to the polysaccharide portion of LPS?
Teichoic acid
204
What is the bacterial cell wall?
A complex, semirigid structure responsible for the shape of the cell that surrounds the fragile plasma membrane and protects the cell from adverse environmental changes.
205
How do prokaryotic cell walls differ from eukaryotic cell walls?
Prokaryotic cell walls differ chemically, are more complex, and are more rigid than the cell walls of plants, algae, and fungi.
206
What is peptidoglycan?
A macromolecular network (also called murein) that makes up the bacterial cell wall, present alone or combined with other substances.
207
What molecules make up the carbohydrate backbone of peptidoglycan?
Alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
208
What type of molecules are NAG and NAM?
Carbohydrates
209
How are NAG and NAM linked together?
By a β-1,4 linkage.
210
What links adjacent rows of peptidoglycan together?
Polypeptides (the peptide portion of peptidoglycan).
211
What are tetrapeptide side chains?
Side chains consisting of four amino acids attached to NAM molecules in the peptidoglycan backbone.
212
What is unique about the amino acids in peptidoglycan?
They alternate between D and L forms, unlike proteins, which contain only L-amino acids.
213
How are tetrapeptide side chains connected to each other?
Either directly or by a peptide cross-bridge.
214
How does penicillin affect bacterial cell walls?
It interferes with the final linking of peptidoglycan rows by peptide cross-bridges.
215
What happens to a bacterial cell when penicillin disrupts peptidoglycan linking?
The cell wall is weakened and the cell undergoes lysis due to rupture of the plasma membrane and loss of cytoplasm.
216
What is the structure of a gram-positive cell wall?
Many layers of peptidoglycan forming a thick, rigid structure.
217
What is the periplasmic space in gram-positive bacteria?
The space between the cell wall and plasma membrane; it contains a granular layer composed of lipoteichoic acid.
218
What are teichoic acids?
Molecules made primarily of an alcohol (glycerol or ribitol) and phosphate found in gram-positive cell walls.
219
What are the two classes of teichoic acids?
Lipoteichoic acid: spans the peptidoglycan and is linked to the plasma membrane
Wall teichoic acid: linked directly to peptidoglycan
220
What functions do teichoic acids serve?
Regulate movement of cations due to negative charge
Help prevent cell lysis
Aid in cell growth
Provide antigenic specificity for laboratory identification
221
What is the basic structure of a gram-negative cell wall?
One or very few layers of peptidoglycan
An outer membrane
222
Where is peptidoglycan located in gram-negative bacteria?
In the periplasm, between the outer membrane and plasma membrane.
223
What does the periplasm of gram-negative bacteria contain?
A gel-like fluid with high concentrations of degradative enzymes and transport proteins.
224
Do gram-negative bacteria contain teichoic acids?
No
225
Why are gram-negative bacteria more susceptible to mechanical breakage?
Because they contain only a small amount of peptidoglycan.
226
What is the outer membrane of gram-negative bacteria composed of?
Lipopolysaccharides (LPS), lipoproteins, and phospholipids.
227
lipopolysaccharide (LPS)
A large, complex molecule in the outer membrane of gram-negative bacteria that contains lipids and carbohydrates.
228
What are the three components of LPS?
Lipid A
Core polysaccharide
O polysaccharide
229
What is lipid A?
The lipid portion of LPS that is embedded in the top layer of the outer membrane.
230
What happens to lipid A when gram-negative bacteria die?
Lipid A is released.
231
What is the function of released lipid A?
It functions as an endotoxin.
232
What symptoms are caused by lipid A?
Fever
Dilation of blood vessels
Shock
Blood clotting
233
Where is the core polysaccharide located in LPS?
Attached to lipid A.
234
What does the core polysaccharide contain?
Unusual sugars
235
What is the role of the core polysaccharide?
Structural — to provide stability to the LPS.
236
Where does the O polysaccharide extend from?
Outward from the core polysaccharide.
237
What is the O polysaccharide composed of?
Sugar molecules.
238
What is the function of the O polysaccharide?
It functions as an antigen.
239
Why is the O polysaccharide clinically important?
It is useful for distinguishing serovars of gram-negative bacteria.
240
What gram-positive structure has a comparable antigenic role to the O polysaccharide?
Teichoic acids
241
What is the periplasmic space?
Space between membranes
242
What is present in the periplasmic space?
Water
243
What major process occurs in the periplasmic space?
Transport
244
How would you describe the activity level of the periplasmic space?
Very active space
245
What is the Gram stain mechanism based on?
Differences in the cell wall structure of gram-positive and gram-negative bacteria and how they react to staining reagents.
246
What does crystal violet stain?
Both gram-positive and gram-negative cells purple by binding to peptidoglycan.
247
What is the role of iodine in the Gram stain?
It acts as a mordant, forming large crystal violet–iodine complexes that are not soluble in water.
248
What effect does alcohol have during Gram staining?
It dissolves the outer membrane of gram-negative cells and washes the crystal violet–iodine complex out of their thin peptidoglycan layer.
249
Why are gram-negative cells colorless after the alcohol wash?
The crystal violet–iodine complex is removed from their thin peptidoglycan layer.
250
What is the role of safranin in the Gram stain?
It acts as a counterstain, turning gram-negative cells pink or red.
251
Why do gram-positive cells remain purple after safranin is applied?
The darker purple crystal violet already retained in the thick peptidoglycan masks the safranin color.
252
Why might some gram-positive cells stain gram-negative?
They are usually dead.
253
What does “gram-variable” mean?
Some gram-positive bacteria show an increasing number of gram-negative cells as the culture ages.
254
Which genera are examples of gram-variable bacteria?
Bacillus and Clostridium.
255
What does atypical cell wall mean?
Cell wall structure differs from typical Gram-positive or Gram-negative bacteria
256
Name two important species of Mycobacterium
Mycobacterium tuberculosis and Mycobacterium leprae
257
What unique substance found in the Mycobacterium cell wall
Mycolic acid
258
Were is mycolic acid location in Mycobacterium
Extra layer on top of the normal cell wall
259
How does mycolic acid effect on staining
Changes staining; cannot stain like other organisms
260
Does Mycoplasma have a cell wall?
No, completely lacks a wall
261
How is Mycoplasma cell stabilized without a wall?
Very solid plasma membrane
262
What important component is found in the Mycoplasma membrane
Sterols
263
Is Mycoplasma used for staining?
No
264
What disease is caused by Mycoplasma?
Pneumonia
265
Do Archaea typically have a bacterial cell wall?
No wall or false wall
266
Can Archaea make peptidoglycan?
No, cannot make peptidoglycan
267
How many stains are used in a simple stain?
One stain
268
What type of stain is used in a simple stain?
One basic stain
269
What is a simple stain used to determine?
Shape, arrangement, and size
270
Mordant
271
What is the function of a mordant?
Intensifies stain
272
How does a mordant intensify staining?
Thickens stain around cells
273
Differential Stains
274
How long does a Gram stain take?
~5 minutes
275
How difficult is the Gram stain?
Very easy stain
276
Who developed the Gram stain?
Christian Gram
277
What does the Gram stain differentiate?
Gram-positive and Gram-negative bacteria
278
What is the first step in the Gram stain?
Crystal violet (basic stain)
279
What is the second step in the Gram stain?
Iodine (mordant)
280
What is the decolorizer used in Gram staining?
95% ethanol or acetone
281
How long should the decolorizer be applied?
10–30 seconds ONLY
282
What is the counterstain in the Gram stain?
Safranin
283
What color are Gram-positive bacteria after staining?
Purple
284
Why do Gram-positive bacteria stay purple?
CV–iodine complex is trapped
285
What happens to Gram-negative bacteria during Gram staining?
Become colorless, then pink/red
286
Why don’t all bacteria retain the stain?
Based on cell wall structure
287
Acid-Fast Stain
288
What primary stain is used in the acid-fast stain?
Carbolfuchsin
289
What color is carbolfuchsin?
Dark red
290
Does the acid-fast stain require heat?
Yes
291
How long is heat applied in acid-fast staining?
5–10 minutes
292
How does sample age affect heating time?
Fresher sample = less heating Older sample = more heating
293
What type of heat source is used?
Steam, not flame
294
What works best for heating?
Boiling water
295
Acid-Fast — Decolorizer & Counterstain
296
What decolorizer is used in acid-fast staining?
Acid-alcohol (very strong)
297
What is the counterstain in acid-fast staining?
Methylene blue
298
Acid-Fast — Results
299
What color are acid-fast positive cells?
Red
300
What color are acid-fast negative cells?
Blue
301
What prevents acid-fast bacteria from being decolorized?
Mycolic acid
302
What color do TB cells always remain?
Red
303
Special Stains
304
What type of stain is a capsule stain?
Acidic stain
305
What does a capsule stain color?
Background, not cells
306
Why is water washing dangerous in capsule staining?
Can break the capsule
307
What are the colors seen in a capsule stain?
Blue background with red cells
308
How does a capsule appear in staining?
Halo around the cell
309
What does a partial halo indicate?
Capsule dislodged
310
Endospore Stain
311
What is an endospore?
Survival structure
312
Are endospores used for reproduction?
No
313
What color does everything turn in an endospore stain?
Green
314
Does the endospore stain require heat?
Yes (boiling water)
315
Why is the flagella stain challenging?
Flagella are very delicate
316
What dye is used in the flagella stain?
Red dye
317
What mordant is used in the flagella stain?
Potassium alum
318
Why must the flagella stain be done quickly?
Fragility of flagella
319
What is a lysozyme
Part of the immune system
320
Where is lysozyme found in the body?
Tears, saliva, mucus, and breast milk
321
What part of the bacterial cell wall does lysozyme break?
Glycan portion
322
What happens to Gram-positive bacteria when exposed to lysozyme?
Forms a protoplast → cell death
323
What happens to Gram-negative bacteria when exposed to lysozyme?
Forms a spheroplast → cell death
324
What part of the bacterial cell wall does penicillin destroy?
Peptide linkages
325
Why is penicillin more effective against Gram-positive bacteria?
Thick peptidoglycan layer
326
Is penicillin more or less effective against Gram-negative bacteria?
Less effective
327
How does the bacterial plasma membrane compare to the human cell membrane?
Same as human cell
328
What processes occur at the plasma membrane?
Osmosis and diffusion
329
What solution conditions relate to plasma membrane movement?
Isotonic and hypotonic
330
Is the bacterial cytoplasm divided into compartments?
No division
331
How many organelles are found in bacterial cytoplasm?
Only one organelle
332
What is the nucleoid?
DNA region
333
What type of ribosomes do prokaryotes have?
70S ribosomes
334
How do prokaryotic ribosomes compare in size to eukaryotic ribosomes?
Smaller
335
Why are ribosomes important targets for antibiotics?
Antibiotics target ribosomes
336
What structures are discussed after the prokaryotic cell wall?
The plasma membrane and components within the cytoplasm of the prokaryotic cell.
337
What is the plasma (cytoplasmic) membrane?
A thin structure lying inside the cell wall that encloses the cytoplasm of the cell.
338
What is another name for the plasma membrane?
The inner membrane.
339
What are the main chemical components of the prokaryotic plasma membrane?
Primarily phospholipids and proteins.
340
What additional components are found in eukaryotic plasma membranes but not usually in prokaryotic membranes?
Carbohydrates and sterols (such as cholesterol).
341
Why are prokaryotic plasma membranes less rigid than eukaryotic membranes?
Because they lack sterols.
342
What is the exception to prokaryotes lacking membrane sterols?
Wall-less prokaryotes of the genus Mycoplasma, which contain membrane sterols.
343
How are plasma membranes structurally arranged?
As two-layered structures.
344
What is the name of the two-layered arrangement of phospholipids?
A lipid bilayer.
345
How are phospholipid molecules arranged in the lipid bilayer?
In two parallel rows.
346
What components make up the polar head of a phospholipid?
A phosphate group and glycerol.
347
What property makes the phospholipid head interact with water?
It is hydrophilic (water-loving) and soluble in water.
348
What are the nonpolar tails of a phospholipid made of?
Fatty acids.
349
What property makes phospholipid tails avoid water?
They are hydrophobic (water-fearing) and insoluble in water.
350
Where are the polar heads and nonpolar tails located in the lipid bilayer?
Polar heads face the two surfaces of the bilayer, and nonpolar tails face the interior.
351
In a prokaryotic cell, what does the term cytoplasm refer to?
The substance of the cell inside the plasma membrane.
352
Approximately what percentage of the cytoplasm is water?
About 80%.
353
What are the main components found in the cytoplasm?
Proteins (enzymes), carbohydrates, lipids, inorganic ions, and many low-molecular-mass compounds.
354
How do inorganic ion concentrations in cytoplasm compare to most media?
They are present in much higher concentrations in the cytoplasm.
355
How is cytoplasm described physically?
Thick, aqueous, semitransparent, and elastic.
356
What are the major structures found in the cytoplasm of prokaryotes?
The nucleoid (containing DNA), ribosomes, and inclusions.
357
What is the cytoskeleton?
A collective term for a series of fibers (small rods and cylinders) in the cytoplasm.
358
What was previously believed about the cytoskeleton in prokaryotes?
That prokaryotes lacked a cytoskeleton.
359
What evidence showed that prokaryotic cells have a cytoskeleton?
Atomic force microscopy.
360
Name the main components of the prokaryotic cytoskeleton.
MreB, ParM, crescentin, and FtsZ.
361
To which eukaryotic cytoskeletal elements do prokaryotic cytoskeleton proteins correspond?
MreB → microfilaments, ParM → intermediate filaments, FtsZ → microtubules.
362
What roles does the prokaryotic cytoskeleton play?
Cell division, maintaining cell shape, growth, DNA movement, and alignment of inclusions.
363
What is the nucleoid?
The region of a bacterial cell that contains its DNA.
364
What type of DNA is found in the nucleoid?
A single long, continuous, frequently circular, double-stranded DNA molecule.
365
What is the bacterial chromosome?
The DNA contained within the nucleoid.
366
How does the bacterial chromosome differ from eukaryotic chromosomes?
It is not surrounded by a nuclear envelope and does not contain histones.
367
What shapes can the nucleoid have?
Spherical, elongated, or dumbbell-shaped.
368
What cellular structure is responsible for protein synthesis?
Ribosomes.
369
Which types of cells contain ribosomes?
All eukaryotic and prokaryotic cells.
370
What type of cells have a large number of ribosomes?
Cells with high rates of protein synthesis, such as actively growing cells.
371
What effect do ribosomes have on the appearance of prokaryotic cytoplasm?
They give the cytoplasm a granular appearance.
372
What are ribosomes composed of?
Two subunits made of protein and ribosomal RNA (rRNA).
373
What type of RNA is found in ribosomes?
Ribosomal RNA (rRNA).
374
How do prokaryotic ribosomes differ from eukaryotic ribosomes?
They contain different numbers of proteins and rRNA molecules and are smaller and less dense.
375
What are prokaryotic ribosomes called?
70S ribosomes.
376
What are eukaryotic ribosomes called?
80S ribosomes.
377
What are inclusions in prokaryotic cells?
Reserve deposits found within the cytoplasm of prokaryotic cells.
378
Why do cells form inclusions?
To accumulate nutrients when they are plentiful and use them when the environment is deficient.
379
What advantage is suggested by concentrating macromolecules in inclusions?
It avoids an increase in osmotic pressure that would occur if the molecules were dispersed in the cytoplasm.
380
Are inclusions found in all bacteria?
Some inclusions are common to many bacteria, while others are limited to a small number of species.
381
Why can certain inclusions be useful for identification?
Because some inclusions are limited to specific species and serve as a basis for identification.
382
What are magnetosomes enclosed by?
A membrane derived from the plasma membrane.
383
What are carboxysomes enclosed by?
Protein complexes.
384
What are endospores?
Specialized, highly durable, dehydrated “resting” cells formed by certain bacteria.
385
Are endospores unique to bacteria?
Yes, endospores are unique to bacteria.
386
Where are endospores formed within the cell?
Internally, within the bacterial cell membrane.
387
What diseases are caused by some Clostridium species?
Gangrene, tetanus, botulism, and food poisoning.
388
What diseases are caused by some Bacillus species?
Anthrax and food poisoning.
389
What environmental extremes can endospores survive?
Extreme heat, lack of water, toxic chemicals, and radiation.
390
How long can endospores remain dormant?
Thousands of years.
391
Why are endospores clinically important?
They resist processes that normally kill vegetative cells.
392
Why are endospores a problem in the food industry?
They can survive underprocessing and later grow and produce toxins.
393
Typical size of a prokaryotic cell?
~0.2–2.0 µm in diameter
394
Typical size of a eukaryotic cell?
~10–100 µm in diameter
395
Do prokaryotic cells have a nucleus?
No true nucleus; no nuclear membrane or nucleoli
396
Do eukaryotic cells have a nucleus?
Yes; true nucleus with nuclear membrane and nucleoli
397
Do prokaryotic cells contain membrane-enclosed organelles?
No; relatively few internal structures
398
Do eukaryotic cells contain membrane-enclosed organelles?
Yes; examples include nucleus, lysosomes, Golgi complex, ER, mitochondria, chloroplasts
399
Structure of prokaryotic flagella?
Consist of two protein building blocks
400
Structure of eukaryotic flagella?
Complex; composed of multiple microtubules
401
Glycocalyx in prokaryotic cells?
Present as a capsule or slime layer
402
Glycocalyx in eukaryotic cells?
Present in some cells that lack a cell wall
403
Cell wall composition in prokaryotic cells?
Usually present; chemically complex (bacterial cell wall contains peptidoglycan)
404
Cell wall composition in eukaryotic cells?
When present, chemically simple (cellulose in plants; chitin in fungi)
405
Plasma membrane characteristics in prokaryotes?
Carbohydrates and generally lacks sterols
406
Plasma membrane characteristics in eukaryotes?
Sterols and carbohydrates that serve as receptors
407
Cytoplasm features in prokaryotic cells?
Cytoskeleton present (MreB, ParM, crescentin, FtsZ); no cytoplasmic streaming
408
Cytoplasm features in eukaryotic cells?
Cytoskeleton (microfilaments, intermediate filaments, microtubules); cytoplasmic streaming
409
Ribosome size in prokaryotic cells?
70S ribosomes
410
Ribosome size in eukaryotic cells?
80S ribosomes (70S in organelles)
411
Chromosome structure in prokaryotic cells?
Usually single circular chromosome; typically lacks histones
412
Chromosome structure in eukaryotic cells?
Multiple linear chromosomes with histones
413
Type of cell division in prokaryotes?
Binary fission
414
Type of cell division in eukaryotes?
Mitosis
415
Sexual recombination in prokaryotes?
None; transfer of DNA only
416
Sexual recombination in eukaryotes?
Involves meiosis
417
Greek word for prokaryote
Prokaryote comes from Greek words meaning pre-nucleus.
418
Greek word for eukaryote
Eukaryote comes from Greek words meaning true nucleus.
419
What does prokaryote mean?
Pre-nucleus
420
What type of chromosome do prokaryotes have?
One circular chromosome, not in a membrane
421
Do prokaryotes have organelles?
No organelles
422
What type of cell wall do prokaryotes have?
Peptidoglycan cell walls
423
How do prokaryotes reproduce?
Binary fission
424
What does eukaryote mean?
True nucleus
425
What type of chromosomes do eukaryotes have?
Paired chromosomes, in nuclear membrane
426
Do eukaryotes have organelles?
Several organelles
427
What type of cell walls do eukaryotes have?
Simple cell walls
428
How do eukaryotes divide?
Mitosis, meiosis
429
WHat does bacillus / Bacillus mean
Can be used as a scientific name or to describe a shape
430
what is a single bacillus
One rod-shaped cell
431
what is a diplobacilli
Two bacilli together
432
what is a streptobacilli
Chains of bacilli
433
What is a coccus?
A spherical (round) bacterial shape
434
What bacterial arrangements are classified as pairs?
Diplococci, diplobacilli
435
What bacterial arrangement forms clusters?
Staphylococci
436
What bacterial arrangements form chains?
Streptococci, streptobacilli
437
Where is the glycocalyx (capsule) located?
Outside cell wall
438
What is the glycocalyx (capsule) usually like?
Usually sticky
439
What effect does the glycocalyx (capsule) have on virulence?
Increases virulence
440
What does the glycocalyx (capsule) allow bacteria to do?
Allows bacterial cell to attach
441
What immune process do capsules prevent?
Phagocytosis
442
What is the flagellar filament made of?
Chains of flagellin
443
What is the flagellum attached to?
A protein hook
444
How is the flagellum anchored?
Anchored to the wall and membrane by the basal body
445
What are axial filaments also called?
Endoflagella
446
In what type of bacteria are axial filaments found?
Spirochetes
447
Where are axial filaments anchored?
At one end of a cell
448
What is the function of axial filaments?
Propel the bacteria in a spiral motion
449
What is the cell wall made of?
peptidoglycan
450
What is peptidoglycan (murein)
A polymer of a disaccharide
451
What two molecules make up the disaccharide in peptidoglycan?
N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
452
What does NAG stand for?
N-acetylglucosamine
453
What does NAM stand for?
N-acetylmuramic acid
454
How many layers of peptidoglycan are in a gram-negative cell wall?
One or two layers of peptidoglycan
455
What type of bilayer is part of the gram-negative outer membrane?
Phospholipid bilayer
456
What proteins are found in the gram-negative outer membrane that allow passage?
Porins (proteins)
457
What type of proteins connect the outer membrane to the cell wall in gram-negative bacteria?
Lipoproteins
458
What major molecule is found in the gram-negative outer membrane that contributes to toxicity?
Lipopolysaccharides
459
Which part of lipopolysaccharide is an endotoxin?
Lipid A
460
What is the other component of lipopolysaccharides listed on the slide?
O-polysaccharide
461
What is the periplasmic space?
A very active area of cell metabolism
462
Where is the periplasmic space located?
Between the outer membrane and the plasma membrane
463
What are the main features of a gram-positive cell wall?
Thick peptidoglycan
Teichoic acids
464
What is the thickness of peptidoglycan in gram-positive bacteria?
Thick peptidoglycan
465
What acids are found in the gram-positive cell wall?
Teichoic acids
466
What are the main features of a gram-negative cell wall?
Thin peptidoglycan
Outer membrane
Periplasmic space
467
How does peptidoglycan thickness differ in gram-negative bacteria?
Thin peptidoglycan
468
What extra structural features are present in gram-negative cell walls but not listed for gram-positive?
Outer membrane
Periplasmic space
469
What forms inside the cell during the Gram stain?
Crystal violet–iodine (CV-I) crystals
470
What does alcohol do in gram-positive cells during Gram staining?
Alcohol dehydrates peptidoglycan
471
What happens to CV-I crystals in gram-positive cells?
CV-I crystals do not leave
472
What does alcohol do in gram-negative cells during Gram staining?
Alcohol dissolves the outer membrane and leaves holes in peptidoglycan
473
What happens to CV-I crystals in gram-negative cells?
CV-I washes out
474
What type of lipid is found in acid-fast cell walls?
Waxy lipid (mycolic acid)
475
Mycolic acid in acid-fast cell walls is bound to what?
Peptidoglycan
476
Which bacterial group has acid-fast cell walls?
Mycobacterium species
477
What do Mycoplasma lack?
Cell walls
478
What is found in the plasma membrane of Mycoplasma?
Sterols
479
What types of cell walls do Archaea have?
Wall-less or walls of pseudomurein
480
What enzyme digests the disaccharide in peptidoglycan? Resulting in cell wall damage
Lysozyme
481
What does lysozyme digest in the cell wall? * Damage to cell wall
The disaccharide in peptidoglycan
482
What is a protoplast? * Damage to cell wall
A wall-less gram-positive cell
483
How is a protoplast formed? *Damage to cell wall
By the action of lysozyme
484
What is a spheroplast? *Damage to cell wall
A structure formed by the action of lysozyme on a gram-negative cell
485
What does penicillin inhibit in peptidoglycan? That results in damage to the cell wall
Peptide bridges
486
What does the plasma membrane have?
A phospholipid bilayer
487
What types of proteins are found in the plasma membrane?
Peripheral proteins and integral proteins
488
What property does the plasma membrane exhibit?
Selective permeability
489
What does selective permeability allow?
Passage of some molecules
490
What is simple diffusion?
Movement of a solute from an area of high concentration to an area of low concentration
491
In simple diffusion, what moves across the membrane?
A solute
492
In simple diffusion, what is the direction of movement?
From high concentration to low concentration
493
facilitated diffusion
Solute combines with a transporter protein in the membrane
494
In facilitated diffusion, what does the solute combine with?
A transporter protein
495
Where is the transporter protein located in facilitated diffusion?
In the membrane
496
osmosis
The movement of water across a selectively permeable membrane from an area of high water to an area of lower water concentration
497
What moves during osmosis?
Water
498
Osmosis occurs across what type of membrane?
A selectively permeable membrane
499
During osmosis, water moves from an area of ___ water concentration to ___ water concentration.
High → lower
500
What is cytoplasm?
The substance inside the plasma membrane
501
What does the nucleiod contain?
contains the bacterial chromosome
502
What happens to water in an isotonic solution?
No net movement of water
503
In a hypotonic solution, which direction does water move?
Water moves into the cell
504
What happens to a cell in a hypotonic solution if the cell wall is strong?
It contains the swelling
505
What happens to a cell in a hypotonic solution if the cell wall is weak or damaged?
The cell bursts (osmotic lysis)
506
In a hypertonic solution, which direction does water move?
Water moves out of the cell
507
What happens to the cytoplasm in a hypertonic solution?
The cytoplasm shrinks (plasmolysis)
508
What is the function of the prokaryotic ribosome?
Protein synthesis.
509
What is the size of a prokaryotic ribosome?
70S.
510
What subunits make up the 70S prokaryotic ribosome?
A 50S subunit and a 30S subunit.
511
What is the large subunit of the prokaryotic ribosome called?
50S subunit.
512
What is the small subunit of the prokaryotic ribosome called?
30S subunit.
513
What are endospores?
Resting cells.
514
What are endospores resistant to?
Desiccation, heat, and chemicals.
515
Which bacterial genera form endospores?
Bacillus and Clostridium species.
516
What is the exception for endospore formation?
Bacillus anthracis
→ Does NOT form endospores inside the host (sporulates only outside the body)
517
What is sporulation?
Endospore formation.
518
What is germination?
Return to vegetative state.
519
What is sporulation?
The process of endospore formation.
520
What begins the formation of an endospore in step 1?
A spore septum begins to isolate newly replicated DNA and a small portion of cytoplasm.
521
What happens in step 2 of endospore formation?
The plasma membrane starts to surround the DNA and cytoplasm isolated in step 1.
522
What structure is formed in step 3 of sporulation?
The spore septum surrounds the isolated portion, forming a forespore.
523
What forms between the two membranes in step 4?
A peptidoglycan layer.
524
What develops in step 5 of endospore formation?
The spore coat forms.
525
What happens in the final step (step 6)?
The endospore is freed from the cell.
Microbiology
flashcards
Decks in class (20)
# Cards
